Metallic finish



Patented July 13, 1937 METALLIC FINISH John Dorman'McBurney, Newburgh,N. 'Y., and

Edgar Hugo Nollau, Wilmington, Del, assignors to E. I. du Pont deNemours & Company, Wilmington, DeL, a corporation of Delaware NoDrawing. Application March 21, 1936, Serial No. 70,106

8 Claims.

This invention relates to metallic surface coated articles having highlylustrous finishes, and especiallyto the production of such coatings bymeans of metallic powders.

This case is a, continuation in part of our 00- pending cases SerialNos. 661,418 and 705,618 filed March 17, 1933 and January 9, 1934,respectively.

Heretofore lustrous metallic surfaced articles have been produced byadhering to or combining with a base material one of'the various metalfoils which has been highly polished or otherwise suitably surfaced. Bythe term metal foil is meant a continuous sheet of metal having anapproximate thickness from 0.0001 to 0.05 of an inch, but the thicknessmay be varied in special circumstances and thicker or thinner sheets maybe included in the class. generally as metallic covered articles, asmetallic covered papers or metallic'covered fabrics and the like, andthey are used for various-purposes.

It is among the objects of the invention to provide articles with afinish of high metallic luster. Another object of the invention is toprovide methods whereby metallic powders may be used to produce highlylustrous or mirror-like metallic finishes. L

Other objects of the invention will be apparent in connection-with thefollowing description.

The objects of the invention are attained generally by applyingleaf-like particles of reflective 'metal to the surface to be treated,suitably causing them to adhere thereto; and applying orienting andlustre-producing operations whereby the particles are brought intoposition and condition to give a lustrous mirror-like surfaceappearance. The particles of metal powder may desirably have highlyreflective surfaces. The invention is illustrated by the followingembodiments.

Example I To a suitable paper base, for example, such a paper as thathaving the trade name Gloscote, is applied one coat of an anchoringcomposition consisting of 43.8% of a China-w'ood-linseed oil modifiedpolyhydric alcohol-'polybasic acid resin, 53.5% of thinner consisting ofa mixture of mineral thinner and high flash naphtha, and a quantity ofcobalt and manganese drier (introduced a as linoleate) which correspondsto 0.1% metalhe cobalt and 0.1 ;.v metallic manganese based on Thesearticles are known the drying oil content of the resin. The detailedformulation of this composition is as follows:

Solids 43.88 {13.74 9.87

Thinner 53.13

Drier Soi- 1.93%

Following the application of this composition by means of a doctor knifewhereby 0.4-2.0 ounces per square yard are deposited, the coatedmaterial is passed through a '72 foot drying chamber heated by steamcoils so that a temperature of 15 -200 F. is realized, forced draftbeing employed during the operation to remove the solvent vapors. Therate of coating is five yards per minute. After leaving the dryingchamber, the coated surface is brought into contact with alu- 20 minumpowder and the excess powder is then removed by mechanical buflingequipment composed of a series of oppositely revolving brushes.

Following a second brushing treatment in a simi- 25 lar buflingequipment, the material is baked by fe'stooning in a chamber at atemperature of approximately F. for a period of two hours and is thenready for use. The finished product is a sheet resembling a metal foilsurface of high luster which can be embossed or printed.

No limitation is placed on the specific method of drying the material.In this and other examples, instead of festooning the material, it maybe passed over a series 01' heating coils or drums. 35 Very good resultshave been obtained by passing the coated material over two'heated drumshaving diameters of 5 and 7 feet, respectively. The two Example II To asuitable rigid base, for example, sheet 50 steel, is appliedone coat ofthe following anchoring composition: 1

mineral thinner Manganese linoleate solution Drier 801. 2.99%

in mineral thinner Following the application of this composition bymeans of a doctor knife, or other suitable means, whereby 0.4 to 2.0ouncesper square yard is deposited, the coated material is passed at aspeed of 15 feet per minute through a '72 foot drying chamber heated to180-200 F. Forced draft is employed during the operation to remove thesolvent vapors. After leaving the drying chamber, the coated surface;while still very slightly tacky, "is brought into contact with aluminumpowder and the excess powder is removed by mechanical bufling equipment,One particularly suitable type is composed of a series of oppositelyrevolving brushes. Following the second brushing, the material istreated as indicated in Example I. The finished product is a sheet ofhigh luster resembling a metal foil surface. It may be embossed orprinted.

In the foregoing examples the coatings of anchoring composition arecured until the surfaces are just tacky enough to retain an adherentthin layer of the metallic powder. Although some of the powder is everso slightly embedded in the coating, the layer of powder is so thin andthe cure of the coating is such that substantially all the particlesconstitute an adherent or surface layer so that when further brushingoperations are performed the particles are arranged flatwise which mayor may not be in overlapping relation on the surface of the coating. Thedegree of cure or tack of the coating must admit of the subsequentbrushing and luster-producing operations. It very nearly approximates ormay beidentical with that which is known as dust free as defined by H.A. Gardner on Page 110 of Physical and Chemical Examination of Paints,Lacquers and Varnishes (1927). This publication describes the conditionof dust free as that at which the finger can be drawn lightly over thesurface of the coating without the same feeling sticky.

In brushing the powder meiit is applied, the

first set of brushes assists in sweep n of! the excess of powder andadherently fixing or slightly embedding"the'particles on the surface asreferrerito above but other means of removing the execs of powder may beused. The second or acids, and 27.2 parts by weight of phthalicanhydride' to a temperatureof 200-225 C. in a vessel fitted with areflux condenser, stirringdevice, and temperaturerecording'instmmentpuntil the acid number of the resulting product-lsless than 10. Other proportions of oil maybe used as for example byheating 17.0 parts by weight of glycerol, 28.0 parts by weight ofChina-wood oil acids, and 27.0 parts by weight of phthalic anhydride toa temperature of 200225 C. until the acid number of the product is under50, at which point 10 to 20 parts of a solvent for the resulting resinis added to cool the hot reaction mixture and thus reduce the reactionrate. The solvent added may be toluene,-xylene, ethyl acetate, butylacetate, gasoline, or the like.

Although sheet steel and paper are recited in the foregoing examples asthe base materials,

many other flexible as well as semi-flexible and rigid base materialscan be used, such as cardboard, wood, Prestwood, "Celotex", leather,regenerated cellulose, cellulose derivative articles such as thoseprepared from the nitrate, acetate, propionate and other esters, as wellas ethyl and benzyl cellulose and other ethers. A coated fabric in whicha cellulose nitrate composition is used to coat the fabric may alsoreceive the high luster metallic surface by means of the process of thisinvention. It is desirable that the base to receive the high lustermetallic surface should be smooth.

Other adhesives or anchoring compositions than those mentioned in theexamples can be used such as mixtures of rosin modifiedphenolformaldehyde resin and oil modified polyhydrlcalcohol-polybasicacid resin, or varnishes of the linseed or China-wood oil type may beused. Cellulose nitrate adhesives may also be used: one containing about4 parts by weight of cellulose nitrate to one part by weight of asoftener, such as di-butyl phthalate, dispersed in suitable media, suchas methyl, ethyl, butyl or amyl acetate, methyl or ethyl alcohol, withor without the addition of aromatic or straight chain hydrocarbons isparticularly useful. Such compositions are well known to those versed inthe coating art and are merely mentioned as examples and not by way ofrestriction.

The adhesive composition is applied by any suitable coating means, suchas a doctor knife, roll coating, or spraying, and may be used either asprepared, or thinned with a thinner such as high flash naphtha,petroleumspirits mixture, or the like. vary between 0.4 and 2.0 ouncesper square yard, 0.9 ounces per square yard being preferred.

The described partial drying or curing of the adhesive base maydesirably be done by passing through a heating chamber at temperaturesbetween and 280 F. The particular type of base material will determinethe temperature of the drying chamber, to wit, surfaces which containoils which exude cannot be dried at the temperature of exudation.

In place of the aluminum powder disclosed in the above example, copperbronze, silver bronze, tin bronze, gold bronze, or any other metal ormetallic alloy, in fact, any metal which is capable of being prepared infinely divided flakes or leaflike form may be used. -While thisinvention is well adapted to produce highly reflective surfaces, easilytarnished metals may be used for special artistic effects.

The powder may be applied by means of any suitable dusting equipment,after which the material is subjected to a frictioning or 'burnishingaction, as by brushing the surface with brush rolls revolving inopposite directions. This operation is one of the most important in theThe amount of resin applied may process of this invention in that itmust suitably orient the metallic particles to give the high luster. I

The baking following the brushing operation, or series of brushingoperations, is preferably carried out as indicatedin the examples;Higher or lower temperatures with suitable shorter or longer periods oftime may, however, be used.

The finished product, a metallic surface of extremely high luster, isentirely satisfactory for most purposes, but where desired it may begiven a final treatment with any suitable clear or transparent coatingcomposition.

The product of the present invention may be used for many purposes nowsatisfied by the use of metal foils.- For example, it may be used forproducing high luster metallic finishes on rigid, semi-rigid andflexible surfaces, thus avoiding the necessity of attaching sheets orfoils of metal to the base materials. Materials having the high lustermetallic finish are particularly useful for decorative purposes, butthey are also useful as surface, finishes which-are more resistant toweathering than the unfinished base material. On light-transmitting basematerials such as glass, regenerated cellulose, and cellulose esters andethers, the finish presents a mirror when viewed by reflected lightwhile the material is still semi-transparent to direct light. On woodand plaster casts the finish may be appliedchiefiy for decorativepurposes but it will i also act as a protective covering. Highly orna- Ihereinbefore.

mental effects may be obtained by using colored bronzes, for example,aluminum bronze colored with various organic dyestuffs.

Similarly, the invention may be embodied in ornamental papers, bookjackets, wrapping ma-- terials such as cigarette and food wrappers,moving picture screens, outdoor signs and the like,

As applied to materials which are to be flexed or subjected todistortion, the finish is especially durable as for example againstdamage by flexing or by stretching the base material.

One form of ornamental material may be made by superimposing ornamentalfigures or designs on the base material, or in case the material hasbeen precoated, by superimposing the design on the coating. Theornamental shapes or figures may be made by printing, stamping, paintingor the like, using the coating or anchoring materials heretoforeindicated. The superimposed design of anchoring material is cured to thedust free condition, the metal powder is applied and the'article isfinished in the manner described Inasmuch as the metal powder adheres tothe superimposed design or anchoring material, only that part, of thebase material which is covered bythe anchoring material will be giventhe mirror-like finish by this operation.

However, it will be apparent that the base material may be an uncoatedmaterial or a coated material, the necessary requirement being that thepowder shall be non-adherent to the base material or less adherent tothe base material than to the superimposed design of anchoringmaterial.' In this manner a variety of ornamental eifects can beproduced by the suggested variations in design by the use of differenttypes of base materials so that more or less or none of the powder willadhere to the base material and by varying the kind and color of thepowder.

The product of the present invention combines the advantages of the highluster of a metallic surface with the flexibility and other advantageousproperties of a flexible backing such as a paper or fabric. Aluminumpowder has been applied to paper and other flexible and nonfiexiblematerials as a component of a coating composition. The resultingmetallic surface produced by such compositions does 'not have a highluster and appears under high magnification to be made up of thin,leaflike particles standing on edge and otherwise heterogeneouslydisposed without orientation in any definite direction or fiatwise inoverlapping relation so as to provide the described mirror surface. Thestructure and the appearance of the prior art coatings are highlysuggestive of an etched metallic surface in contrast to the highlypolished or lustrous metallic surface of smooth characterand-mirror-like appearance characteristic of the present invention. Thecombination of metal foil to flexible or semi-rigid base materials,while affording a high luster, is deficient in that the finished productcannot be repeatedly folded without breaking the metal and it is notcom- ,bined so intimately with flexible base material as to have thesame strength as the base material.

Furthermore, such combined products are rather stiff which limits theiruses for many purposes. In the materials produced in accordance with thepresent invention the metal surface is extremely thin and tough, and itbecomes to a great extent an integral part of the base to which it isapplied so that it has substantially the same strength as the basematerial. It is not readily removed by scratching, distorting, orcracking as is the case of metal foil facings. A waterproof surfaceessentially impermeable to gases, grease, and the like is produced bythis highly lustrous oriented metallicffinish. The product further showsadvantages over paper and other materials backed with metal foil in thatthe surface produced in accordance with the invention lends itself muchmore satisfactorily to printing and embossingadvantages obviously ofconsiderable importance in a decorative as well as in a utilitarianmaterial. Thus in various physical characteristics the products of thepresent invention have distinctive desired characteristics of practicalvalue not possessed by coatings composed of foil or powder mixtures ofthe prior art.

As many apparently widely difierent embodi-' ments of this invention maybe made without departing from the spirit and scope thereof,'it is to beunderstood that the invention'is not limited to the specific embodimentsthereof except as defined in the appended claims.

We claim:

l. The method of producing a high metallic luster on rigid surfaces,which comprises applying on said surface an anchoring compositioncontaining about 43.8% China-wood oil-linseed oil modified polyhydricalcohol-polybasic acid resin, about 53.5% thinner, and about 3% driercontaining .l% of cobalt and .l% manganese in the form of linoleate,passing the coated material through a drying chamber heated to -215 F.at a rate such that the composition will be cured therein for about 4.8minutes, removing solvent vapors during the curing, applying a liberaldusting of aluminum powder while the surface is still slightlytacky,'sweeping off the excess powder, buifing the coated surface untila mirror-like finish is produced, baking at approximately 226 F. forapproximately-45 seconds to harden the anchoring composition and coatingthe surface with a clear protective coat.

2. The method of making a mirror-like metallic surface on an articlewhich comprises applying a coating of adhesive to the article, curingthe adhesive until it is in a dust free" condition such as that whichcan be produced as described herein by depositing on sheet steel 0.4 to2.0 ounces per square yard of a composition containing 43.8% ofChina-wood-linseed oil modifled polyhydric alcohol-polybasicacidresin,53.5% of a mixture of mineral thinner and high flash naphthaand the remainder drier solution, and passing the sheet throughapproximately a 72 foot drying chamber heated to 180 to 280 F. at a rateof about feet per minute, distributing over the dust free coating ametal pow- 15 der the individual particles of which have lightreflecting faces, removing non-adherent particles, and brushinglyorienting the adhering particles to bring the light reflecting facesinto the plane of the surface of the coating to form a metallic finishof mirror-like reflectivity.

3. The method of making a mirror-like metallic surface on an articlewhich comprises applying a coating of adhesive to the article, curingthe adhesive until it is in a dust free" condition such as that whichcan be produced as described herein by depositing on sheet steel 0.4 to2.0 ounces per square yard of a composition containing 43.8% ofChina-wood-linseed oil modifled polyhydric alcohol-polybasic acid resin,53.5 of a mixture of mineral thinner and high flash naphtha and theremainder drier solution,'and passing the sheet through a 72 foot dryingchamber heated to 180 to 280 F. at a rate of about 15 feet per minute,distributing over the coating of dust free hardness metal 'powder theindividual particles of which have light reflecting faces, removingnon-adherent particles, brushingly orienting the adhering particles tobring the light reflecting faces into the plane of the sur- 40 face ofthe coating to form a metallic finish of mirror-like reflectivity, andthen heating to harden the coating.

4. The method of making a mirror-like surface on an article whichcomprises coating the article with a coating composition containing as afilm-forming ingredient material selected from the class consisting ofphenol-formaldehyde resins, polyhydric alcohol-polybasic acid resins,

and cellulose nitrate, curing the coating until a "dust free conditionis reached which is just tacky enough to retain a firmly adherent thinlayer of metallic powder, distributing over the tacky coating leaf-likemetallic powder the individual particles of which have light reflectingfaces to procure adherence of a thin layer of the particles over thesurface, removing the nonadherent powder, and brushingly orienting theadhering particles until the reflecting faces thereof are broughtsubstantially into the plane of the surface of the coating and a surfaceof mirror-like reflectivity is produced.

5. The method in accordance with claim 4, in which the article is coatedwith a composition comprising an oil modified polyhydricalcoholpolybasic acid resin.

6. The method in accordance with claim4, in which the metal powdercomprises aluminum.

7. 'I'he method of making an article having a highly polished metallicsurface which comprises applying a coating composition comprising an oilmodified polyhydric alcohol-polybasic acid synthetic resin on a flexiblecellulosic base material of the class which consists of cellulose andcellulose derivatives, hardening the coating until the dust-free stageis reached which is just tacky enough to retain a firmly adherent thinlayer of metallic powder, applying over the coating a dusting of metalpowder, the individual particles of said powder having light reflectingfaces, removing non-adherent particles, orienting in/ overlappingrelation on the surface of the coating the particles adhering to saidsurface to bring the light reflecting faces into a continuous planeparallel to the surface of the coating, and finally hardening thecoating, and applying a clear surface coat thereover. 1

8. The product of claim 4 in which the highly reflective mirror-likefinish comprises a hardened coating composition to which the leaf-likemetallic particles are firmly bonded, said flm'sh being highly resistantto abrasion and cracking.

JOHN DORMAN MCBURNEY. EDGAR HUGO NOLLAU.

